Because we possess a skill to evaluate and enjoy aesthetical subjects. This skill varies from person to person (e.g a tall handsome prince may have a bad looking wife or a beautiful princess may be deeply in love with an ugly hunchback).

In humans, bodily symmetry, particularly exemplified by facial symmetry, is known to be a factor in mate selection, and the knowledge/assumption/whatever is that this is because it is taken as an indication of health and the likelihood to produce viable offspring.

In humans, bodily symmetry, particularly exemplified by facial symmetry, is known to be a factor in mate selection, and the knowledge/assumption/whatever is that this is because it is taken as an indication of health and the likelihood to produce viable offspring.

Staff: Mentor

The biology underlying attraction is not well understood and you should keep in mind the cultural effect. It's not difficult to find examples of different societies (or even the same society at different times) with different standards of beauty, often quite different (small and not at all comprehensive example but compare the first Miss America in to the http://wallpaper.krishoonetwork.com/wp-content/uploads/2014/09/Nina-Davuluri-Img.jpg [Broken]). Point being that one should be very wary trying to find a biological/evolutionary explanation for something that varies so radically between individuals and cultures. Clearly the capacity for attraction is biological but how much of what we find attractive is learnt vs innate is a big question.

There's also this chicken-and-egg problem, because the very fact that your mate is attractive says a lot about the likelihood that your offspring will themselves manage to successfully acquire mates and produce their own offspring. So in a sense, their being attractive - whatever that means in one's cultural context - is enough of an evolutionary reason to be mated with, but of course the beginning of "attractiveness" as a feature of human beings needs explanation.

Despite the caution urged by some other posters in this thread, there are some near-universals in standards of attractiveness. Bodily symmetry is one of those already brought out, but facial "averageness" is a more general and well-demonstrated standard that might cover that. Some things that usually make a person less attractive in many cultural contexts are also often signals of poor health/reproductive capacity - wrinkles and other signs of aging, having an unhealthy body weight, pale or diseased-looking skin, sparse or dull hair, and so forth. It's very clear that cultural norms have an incredible shaping effect on our attractiveness standards - and indeed, being able to signal assimilation by conforming to those norms might also be a signal of social intelligence. But if anything about human nature suggests evolution, our standards of attraction do.

I was thinking about this a while back and came to the obvious conclusion that people must be slowly becoming more attractive as the millennia role by. Then, though, it occured to me that the opposite might well be true: what could actually be evolving is our capacity to be attracted. The more universal our taste, the more babies get made.

Consider some remote tribe. The guy that finds all the available women attractive is at an advantage over the guy that only desires the 'most attractive" individual woman. And his more universal taste is something that would likely get passed down to his more numerous offspring.

By this logic it could be possible that we are actually getting uglier and uglier, but not realizing it because we're more and more attracted to whatever's available.

When considering "fitness" in evolution - consider: fitness for what?
Fitness for survival? But of what?

It is the survival of the trait - if the trait is really good at getting perpetuated, then it will persist.
Consider: many organisms have evolved a short lifespan - is that detrimental to the organism?

In the rest of the animal kingdom, the traits that increase the attractiveness of an individual to members of the opposite sex do not necessarily improve the fitness of the organism.

Due to their sometimes greatly exaggerated nature, secondary sexual characteristics can prove to be a hindrance to an animal, thereby lowering its chances of survival. For example, the large antlers of a moose are bulky and heavy and slow the creature's flight from predators; they also can become entangled in low-hanging tree branches and shrubs, and undoubtedly have led to the demise of many individuals. Bright colorations and showy ornamenations, such as those seen in many male birds, in addition to capturing the eyes of females, also attract the attention of predators. Some of these traits also represent energetically costly investments for the animals that bear them. Because traits held to be due to sexual selection often conflict with the survival fitness of the individual, the question then arises as to why, in nature, in which survival of the fittest is considered the rule of thumb, such apparent liabilities are allowed to persist.

Whether these traits that arise and are maintained by sexual selection also increase the fitness of the species is still a question without a clear answer (see the wikipedia link above for further discussion). However, the fact remains that not all evolutionary change is adaptive; some evolutionary changes occur simply through random chance (genetic drift), and sometimes these changes occur through sexual selection and are largely orthogonal to adaptation.

Societies with food scarcities prefer larger female body size than societies having plenty of food. In Western society males who are hungry prefer a larger female body size than they do when not hungry.

Studies based in the United States, New Zealand, and China have shown that women rate men with no trunk (chest and abdominal) hair as most attractive, and that attractiveness ratings decline as hirsutism increases.[76][77] Another study, however, found that moderate amounts of trunk hair on men was most attractive, to the sample of British and Sri Lankan women.

I don't think this question is limited to only humans. This is just an amateur hypothesis but I suspect that in species where the female chooses the male, the male they choose is the one with the brighter plumage or who has won a mating ritual. In species where neither sex chooses its mate, but in which the male mates with any available female, for instance dogs, we don't see a significant difference in characteristics between males and females. In my opinion, human females being the more attractive sex indicates that males are predominantly the ones that choose their mate and that part of that choice is based on physical appearance. Could it be that the emergence of a criterion among a population for selecting a mate becomes self reinforcing and perpetuating?

There is much variation to which traits we as humans find attractive. I would propose that focusing on which traits we find universally unattractive would shed more light on the matter.

Actually an article from a few years ago in Scientific American found that an overall concept of beauty is nearly universal and disregards geography, culture, and so-called "race". This study was begun as an extension to the phenomenon that averaging creates beauty. IIRC someone in the early 20th Century was trying to come up with a picture of an average criminal (to prove some pet theory able to predict criminality) and was perplexed that by combining features and averaging the results always looked more appealing than any of the originals.

Perhaps more importantly, the beauty requirement is also apparently biased by gender. The primary attractors to men are youth and beauty while the attractors to women appear to vary with hormonal cycles and include intelligence, ambition and steadfastness (willingness and ability to invest long term in offspring) but the closer to ovulation reduce to a more visceral sense of power - perhaps a hormonal version of "beer goggles" :P